Ecology: Lower montane to páramo and puna; on soil, soil covered rocks, logs, and trunk of tree ferns (Blechnum) and trees. Elevation: 1000-4300 m (Venezuela: ? m, Colombia: 1700-4300 m, Ecuador: 1550-4000 m, Peru: 1000-2450 m, Bolivia: 1400-3520 m, Argentina: 1150 m). Distribution: Mexico, Central America, West Indies, tropical Andes; also North America, Europe, tropical Africa and Asia. Plants from the tropical Andes are assigned to var. fragilis.
A distinguishing feature of Campylopus fragilis, when present, is the presence of brood leaves produced in the leafy comal tuft at the stem apex; additional features, critical for the determination of sterile collections, include the pale green or yellow plants with leaves 4-5 mm long, often shinny in appearance, excurrent costa toothed at the tips, in cross-section ventral hyalocysts thin-walled and lax, mostly higher than wide, upper cells distinctly quadrate or subquadrate, basal cells long rectangular, thin-walled and lax, alar cells absent or weakly developed. Plants from the tropical Andes are assigned to var. fragilis. Synonyms include Campylopus fimbriatus Mitt. and C. tunariensis Herzog.
Specimens: VENEZUELA. Mérida: Ruiz T. 8328 (FLAS). COLOMBIA. Boyacá: Florschütz 4017 [Campylopodes Exsiccatae 158] (MO, etc.); Cundinamarca: Florschütz 3951 [Campylopodes Exsiccatae 153] (MO, etc.); Valle: Churchill & Lynch 19438 (COL, HUA, MO). ECUADOR. Azuay: Løjtnant & Molau 14821 (NY); Napo: 12 Oct 1988, Frahm & Gradstein [Campylopodes Exsiccatae 142] (MO, etc.). PERU. Peru Cusco: P. & E. Hegewald 8840 (MO). BOLIVIA. La Paz: Marko Lewis 79-1210 (MO); Tarija: Churchill 20795 (MO, USZ). ARGENTIA. Tucumán: Churchill & Schiavone 20090 (LIL, MO).